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1
Josephson, R. K. "Dissecting muscle power output". Journal of Experimental Biology 202, n. 23 (1 dicembre 1999): 3369–75. http://dx.doi.org/10.1242/jeb.202.23.3369.
Testo completoAbstract (sommario):
The primary determinants of muscle force throughout a shortening-lengthening cycle, and therefore of the net work done during the cycle, are (1) the shortening or lengthening velocity of the muscle and the force-velocity relationship for the muscle, (2) muscle length and the length-tension relationship for the muscle, and (3) the pattern of stimulation and the time course of muscle activation following stimulation. In addition to these primary factors, there are what are termed secondary determinants of force and work output, which arise from interactions between the primary determinants. The secondary determinants are length-dependent changes in the kinetics of muscle activation, and shortening deactivation, the extent of which depends on the work that has been done during the preceding shortening. The primary and secondary determinants of muscle force and work are illustrated with examples drawn from studies of crustacean muscles.
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Martin, James C. "Muscle Power". Exercise and Sport Sciences Reviews 35, n. 2 (aprile 2007): 74–81. http://dx.doi.org/10.1097/jes.0b013e31803eb0a0.
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Leonard, Patrick. "Muscle power". New Scientist 193, n. 2592 (febbraio 2007): 23. http://dx.doi.org/10.1016/s0262-4079(07)60473-4.
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Carson, Louise. "Muscle power". Equine Health 2011, n. 2 (8 novembre 2011): 16–18. http://dx.doi.org/10.12968/eqhe.2011.1.2.16.
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Tan, Ming A., Franz K. Fuss e Dhanjoo Ghista. "Muscle Power Indexing for Sports Applications(Sports Biomechanics)". Proceedings of the Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2004.1 (2004): 205–6. http://dx.doi.org/10.1299/jsmeapbio.2004.1.205.
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Josephson, R. "Power output from a flight muscle of the bumblebee Bombus terrestris. II. Characterization of the parameters affecting power output". Journal of Experimental Biology 200, n. 8 (1 aprile 1997): 1227–39. http://dx.doi.org/10.1242/jeb.200.8.1227.
Testo completoAbstract (sommario):
1. Length-tension relationships and work output were investigated in the intact, dorso-ventral flight muscle of the bumblebee Bombus terrestris. The muscle is an asynchronous muscle. Like other asynchronous flight muscles, it has high resting stiffness and produces relatively low active force in response to tetanic stimulation. 2. The muscle shows shortening deactivation and stretch activation, properties that result in delayed force changes in response to step changes in length, a phase lag between force and length during imposed sinusoidal strain and, under appropriate conditions, positive work output during oscillatory length change. 3. Work loops were used to quantify work output by the muscle during imposed sinusoidal oscillation. The curves relating net work per cycle with muscle length, oscillatory strain and oscillatory frequency were all roughly bell-shaped. The work-length curve was narrow. The optimum strain for net work per cycle was approximately 3 %, which is probably somewhat greater than the strain experienced by the muscle in an intact, flying bumblebee. The optimum frequency for net work output per cycle was 63 Hz (30 °C). The optimum frequency for power output was 73 Hz, which agrees well with the normal wing stroke frequency if allowance is made for the elevated temperature (approximately 40 °C) in the thorax of a flying bumblebee. The optimal strain for work output was not strongly dependent on oscillation frequency. 4. Resilience (that is the work output during shortening/work input during lengthening) for unstimulated muscle and dynamic stiffness (=stress/strain) for both stimulated and unstimulated muscles were determined using the strain (3 %) and oscillation frequency (64 Hz) which maximized work output in stimulated muscles. Unstimulated muscle is a good energy storage device. Its resilience increased with increasing muscle length (and increasing resting force) to reach values of over 90 %. The dynamic stiffness of both stimulated and unstimulated muscles increased with muscle length, but the increase was relatively greater in unstimulated muscle, and at long muscle lengths the stiffness of unstimulated muscle exceeded that of stimulated muscle. Effectively, dynamic stiffness is reduced by stimulation! This is taken as indicating that part of the stiffness in an unstimulated muscle reflects structures, possibly attached cross bridges, whose properties change upon stimulation.
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Askew, Graham N., e Richard L. Marsh. "Muscle designed for maximum short-term power output: quail flight muscle". Journal of Experimental Biology 205, n. 15 (1 agosto 2002): 2153–60. http://dx.doi.org/10.1242/jeb.205.15.2153.
Testo completoAbstract (sommario):
SUMMARYTake-off in birds at high speeds and steep angles of elevation requires a high burst power output. The mean power output of the pectoralis muscle of blue-breasted quail (Coturnix chinensis) during take-off is approximately 400 W kg-1 muscle, as determined using two independent methods. This burst power output is much higher than has been measured in any other cyclically contracting muscle. The power output of muscle is determined by the interactions between the physiological properties of the muscle, the stimulation regime imposed by the central nervous system and the details of the strain cycle, which are determined by the reciprocal interaction between the muscle properties and the environmental load. The physiological adaptations that enable a high power output to be achieved are those that allow the muscle to develop high stresses whilst shortening rapidly. These characteristics include a high myofibrillar density, rapid twitch contraction kinetics and a high maximum intrinsic velocity of shortening. In addition, several features of the strain cycle increase the power output of the quail pectoralis muscle. First, the muscle operates at a mean length shorter than the plateau of the length/force relationship. Second,the muscle length trajectory is asymmetrical, with 70 % of the cycle spent shortening. The asymmetrical cycle is expected to increase the power output substantially. Third, subtle deviations in the velocity profile improve power output compared with a simple asymmetrical cycle with constant lengthening and shortening rates. The high burst power outputs found in the flight muscles of quail and similar birds are limited to very brief efforts before fatigue occurs. This strong but short flight performance is well-suited to the rapid-response anti-predation strategy of these birds that involves a short flight coupled with a subsequent sustained escape by running. These considerations serve as a reminder that the maximum power-producing capacities of muscles need to be considered in the context of the in vivosituation within which the muscles operate.
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McNitt-Gray, Jill L. "Human Muscle Power". International Journal of Sport Biomechanics 4, n. 2 (maggio 1988): 178–79. http://dx.doi.org/10.1123/ijsb.4.2.178.
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Reid, Kieran F., e Roger A. Fielding. "Skeletal Muscle Power". Exercise and Sport Sciences Reviews 40, n. 1 (gennaio 2012): 4–12. http://dx.doi.org/10.1097/jes.0b013e31823b5f13.
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Blake, Ollie M., e James M. Wakeling. "Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands". Journal of Neurophysiology 114, n. 6 (1 dicembre 2015): 3283–95. http://dx.doi.org/10.1152/jn.00765.2015.
Testo completoAbstract (sommario):
This study investigated the influence of cycle frequency and workload on muscle coordination and the ensuing relationship with mechanical efficiency and power output of human limb movement. Eleven trained cyclists completed an array of cycle frequency (cadence)-power output conditions while excitation from 10 leg muscles and power output were recorded. Mechanical efficiency was maximized at increasing cadences for increasing power outputs and corresponded to muscle coordination and muscle fiber type recruitment that minimized both the total muscle excitation across all muscles and the ineffective pedal forces. Also, maximum efficiency was characterized by muscle coordination at the top and bottom of the pedal cycle and progressive excitation through the uniarticulate knee, hip, and ankle muscles. Inefficiencies were characterized by excessive excitation of biarticulate muscles and larger duty cycles. Power output and efficiency were limited by the duration of muscle excitation beyond a critical cadence (120–140 rpm), with larger duty cycles and disproportionate increases in muscle excitation suggesting deteriorating muscle coordination and limitations of the activation-deactivation capabilities. Most muscles displayed systematic phase shifts of the muscle excitation relative to the pedal cycle that were dependent on cadence and, to a lesser extent, power output. Phase shifts were different for each muscle, thereby altering their mechanical contribution to the pedaling action. This study shows that muscle coordination is a key determinant of mechanical efficiency and power output of limb movement across a wide range of mechanical demands and that the excitation and coordination of the muscles is limited at very high cycle frequencies.
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Sponberg, S., e T. L. Daniel. "Abdicating power for control: a precision timing strategy to modulate function of flight power muscles". Proceedings of the Royal Society B: Biological Sciences 279, n. 1744 (25 luglio 2012): 3958–66. http://dx.doi.org/10.1098/rspb.2012.1085.
Testo completoAbstract (sommario):
Muscles driving rhythmic locomotion typically show strong dependence of power on the timing or phase of activation. This is particularly true in insects' main flight muscles, canonical examples of muscles thought to have a dedicated power function. However, in the moth ( Manduca sexta ), these muscles normally activate at a phase where the instantaneous slope of the power–phase curve is steep and well below maximum power. We provide four lines of evidence demonstrating that, contrary to the current paradigm, the moth's nervous system establishes significant control authority in these muscles through precise timing modulation: (i) left–right pairs of flight muscles normally fire precisely, within 0.5–0.6 ms of each other; (ii) during a yawing optomotor response, left—right muscle timing differences shift throughout a wider 8 ms timing window, enabling at least a 50 per cent left–right power differential; (iii) timing differences correlate with turning torque; and (iv) the downstroke power muscles alone causally account for 47 per cent of turning torque. To establish (iv), we altered muscle activation during intact behaviour by stimulating individual muscle potentials to impose left—right timing differences. Because many organisms also have muscles operating with high power–phase gains ( Δ power / Δ phase ), this motor control strategy may be ubiquitous in locomotor systems.
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Faulkner, J. A., E. Zerba e S. V. Brooks. "Muscle temperature of mammals: cooling impairs most functional properties". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 259, n. 2 (1 agosto 1990): R259—R265. http://dx.doi.org/10.1152/ajpregu.1990.259.2.r259.
Testo completoAbstract (sommario):
Our purpose was to study the effect of a decrease in skeletal muscle temperature on single and repeated shortening, isometric, and lengthening contractions of mammalian skeletal muscles. Fast extensor digitorum longus muscles of mice were studied in situ and in vitro at 25 and 35 degrees C. No difference in isometric force was observed, but maximum and sustained powers were reduced by 40 and 62%, respectively. With cooling, maximum power absorption, which is proportional to the external work required to lengthen the muscle, increased significantly at each velocity of lengthening from 0.5 to 4.0 optimum fiber length/s. The 10 degrees C decrease in muscle temperature produced a decrease in power that was primarily a result of the decrease in the velocity of shortening, whereas the increase in power absorption was likely due to an increase in the number of strongly bound cross bridges resulting from a decreased rate of detachment. During voluntary exercise at decreased muscle temperatures, maximum and endurance performances are inevitably impaired by the decreases in maximum and sustained power of individual motor units.
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Konow, Nicolai, Emanuel Azizi e Thomas J. Roberts. "Muscle power attenuation by tendon during energy dissipation". Proceedings of the Royal Society B: Biological Sciences 279, n. 1731 (28 settembre 2011): 1108–13. http://dx.doi.org/10.1098/rspb.2011.1435.
Testo completoAbstract (sommario):
An important function of skeletal muscle is deceleration via active muscle fascicle lengthening, which dissipates movement energy. The mechanical interplay between muscle contraction and tendon elasticity is critical when muscles produce energy. However, the role of tendon elasticity during muscular energy dissipation remains unknown. We tested the hypothesis that tendon elasticity functions as a mechanical buffer, preventing high (and probably damaging) velocities and powers during active muscle fascicle lengthening. We directly measured lateral gastrocnemius muscle force and length in wild turkeys during controlled landings requiring rapid energy dissipation. Muscle-tendon unit (MTU) strain was measured via video kinematics, independent of muscle fascicle strain (measured via sonomicrometry). We found that rapid MTU lengthening immediately following impact involved little or no muscle fascicle lengthening. Therefore, joint flexion had to be accommodated by tendon stretch. After the early contact period, muscle fascicles lengthened and absorbed energy. This late lengthening occurred after most of the joint flexion, and was thus mainly driven by tendon recoil. Temporary tendon energy storage led to a significant reduction in muscle fascicle lengthening velocity and the rate of energy absorption. We conclude that tendons function as power attenuators that probably protect muscles against damage from rapid and forceful lengthening during energy dissipation.
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Peplowski, M. M., e R. L. Marsh. "Work and power output in the hindlimb muscles of Cuban tree frogs Osteopilus septentrionalis during jumping." Journal of Experimental Biology 200, n. 22 (1 novembre 1997): 2861–70. http://dx.doi.org/10.1242/jeb.200.22.2861.
Testo completoAbstract (sommario):
It has been suggested that small frogs use a catapult mechanism to amplify muscle power production during the takeoff phase of jumping. This conclusion was based on an apparent discrepancy between the power available from the hindlimb muscles and that required during takeoff. The present study provides integrated data on muscle contractile properties, morphology and jumping performance that support this conclusion. We show here that the predicted power output during takeoff in Cuban tree frogs Osteopilus septentrionalis exceeds that available from the muscles by at least sevenfold. We consider the sartorius muscle as representative of the bulk of the hindlimb muscles of these animals, because this muscle has properties typical of other hindlimb muscles of small frogs. At 25 degrees C, this muscle has a maximum shortening velocity (Vmax) of 8.77 +/- 0.62 L0 s-1 (where L0 is the muscle length yielding maximum isometric force), a maximum isometric force (P0) of 24.1 +/- 2.3 N cm-2 and a maximum isotonic power output of 230 +/- 9.2 W kg-1 of muscle (mean +/- S.E.M.). In contrast, the power required to accelerate the animal in the longest jumps measured (approximately 1.4 m) is more than 800 W kg-1 of total hindlimb muscle. The peak instantaneous power is expected to be twice this value. These estimates are probably conservative because the muscles that probably power jumping make up only 85% of the total hindlimb muscle mass. The total mechanical work required of the muscles is high (up to 60 J kg-1), but is within the work capacities predicted for vertebrate skeletal muscle. Clearly, a substantial portion of this work must be performed and stored prior to takeoff to account for the high power output during jumping. Interestingly, muscle work output during jumping is temperature-dependent, with greater work being produced at higher temperatures. The thermal dependence of work does not follow from simple muscle properties and instead must reflect the interaction between these properties and the other components of the skeletomuscular system during the propulsive phase of the jump.
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Suharjana, Suharjana, Eko Priyanto e Japhet Ndayisenga. "Contribution of Leg Power, Arm Power, Stomach Muscle Power, and Back Muscle Power on Jumping Services". International Journal of Human Movement and Sports Sciences 8, n. 5 (ottobre 2020): 240–48. http://dx.doi.org/10.13189/saj.2020.080512.
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Ellington, C. P. "Power and efficiency of insect flight muscle". Journal of Experimental Biology 115, n. 1 (1 marzo 1985): 293–304. http://dx.doi.org/10.1242/jeb.115.1.293.
Testo completoAbstract (sommario):
The efficiency and mechanical power output of insect flight muscle have been estimated from a study of hovering flight. The maximum power output, calculated from the muscle properties, is adequate for the aerodynamic power requirements. However, the power output is insufficient to oscillate the wing mass as well unless there is good elastic storage of the inertial energy, and this is consistent with reports of elastic components in the flight system. A comparison of the mechanical power output with the metabolic power input to the flight muscles suggests that the muscle efficiency is quite low: less than 10%.
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Josephson, R. "Power output from a flight muscle of the bumblebee Bombus terrestris. III. Power during simulated flight". Journal of Experimental Biology 200, n. 8 (1 aprile 1997): 1241–46. http://dx.doi.org/10.1242/jeb.200.8.1241.
Testo completoAbstract (sommario):
1. The work loop approach was used to measure mechanical power output from an asynchronous flight muscle, the dorso-ventral muscle of the bumblebee Bombus terrestris. Measurements were made at the optimum muscle length for work output at 30 °C and at a muscle temperature (40 °C) and oscillatory frequency (141­173 Hz, depending on the size of the animal) characteristic of free flight. Oscillatory strain amplitude was adjusted to maximize power output. 2. There was much preparation-to-preparation variability in power output. Power output in the muscles with the highest values was slightly greater than 100 W kg-1. It is argued that there are many experimental factors which might reduce measured power output below that in the living bumblebee, and no obvious factors which might lead to overestimates of muscle power. The conclusion is that flight muscle in the intact bumblebee can produce at least 100 W kg-1.
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Hilton, Tiffany N., Lori J. Tuttle, Kathryn L. Bohnert, Michael J. Mueller e David R. Sinacore. "Excessive Adipose Tissue Infiltration in Skeletal Muscle in Individuals With Obesity, Diabetes Mellitus, and Peripheral Neuropathy: Association With Performance and Function". Physical Therapy 88, n. 11 (1 novembre 2008): 1336–44. http://dx.doi.org/10.2522/ptj.20080079.
Testo completoAbstract (sommario):
Background and Purpose The primary purpose of this study was to report differences in calf intermuscular adipose tissue (IMAT), muscle strength (peak torque), power, and physical function in individuals with obesity, diabetes mellitus (DM), and peripheral neuropathy (PN) compared with those without these impairments. A secondary purpose was to assess the relationship between IMAT and muscle strength, power, and physical function. Subjects and Methods Six participants with obesity, DM, and PN (2 women, 4 men; mean age=58 years, SD=10; mean body mass index=36.3, SD=5; mean modified Physical Performance Test [PPT] score=22, SD=3) and 6 age- and sex-matched control subjects without these impairments were assessed and compared in muscle strength, muscle power, physical functioning, and muscle and fat volume, including IMAT in the calf muscles. Muscle, adipose tissue, and IMAT volumes of each calf were quantified by noninvasive magnetic resonance imaging. Muscle strength and power of the plantar-flexor and dorsiflexor muscles were quantified using isokinetic dynamometry. The modified PPT was used to assess physical function. Results Leg muscle and fat volumes were similar between groups, although IMAT volumes were 2.2-fold higher in the subjects with obesity, DM, and PN (X̅=120 cm3, SD=47) than in the control subjects (X̅=54 cm3, SD=41). Muscle strength, muscle power, ratio of leg muscle power to leg muscle volume, and modified PPT scores were lower in subjects with obesity, DM, and PN compared with the control subjects. Discussion and Conclusion The data indicate that excess fat infiltration in leg skeletal muscles is associated with low calf muscle strength, low calf muscle power, and impaired physical function in individuals who are obese with DM and PN.
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Roberts, Thomas J., Emily M. Abbott e Emanuel Azizi. "The weak link: do muscle properties determine locomotor performance in frogs?" Philosophical Transactions of the Royal Society B: Biological Sciences 366, n. 1570 (27 maggio 2011): 1488–95. http://dx.doi.org/10.1098/rstb.2010.0326.
Testo completoAbstract (sommario):
Muscles power movement, yet the conceptual link between muscle performance and locomotor performance is poorly developed. Frog jumping provides an ideal system to probe the relationship between muscle capacity and locomotor performance, because a jump is a single discrete event and mechanical power output is a critical determinant of jump distance. We tested the hypothesis that interspecific variation in jump performance could be explained by variability in available muscle power. We used force plate ergometry to measure power produced during jumping in Cuban tree frogs ( Osteopilus septentrionalis ), leopard frogs ( Rana pipiens ) and cane toads ( Bufo marinus ). We also measured peak isotonic power output in isolated plantaris muscles for each species. As expected, jump performance varied widely. Osteopilus septentrionalis developed peak power outputs of 1047.0 ± 119.7 W kg −1 hindlimb muscle mass, about five times that of B. marinus (198.5 ± 54.5 W kg −1 ). Values for R. pipiens were intermediate (543.9 ± 96.2 W kg −1 ). These differences in jump power were not matched by differences in available muscle power, which were 312.7 ± 28.9, 321.8 ± 48.5 and 262.8 ± 23.2 W kg −1 muscle mass for O. septentrionalis , R. pipiens and B. marinus , respectively. The lack of correlation between available muscle power and jump power suggests that non-muscular mechanisms (e.g. elastic energy storage) can obscure the link between muscle mechanical performance and locomotor performance.
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Hikmad Hakim, Anto Sukamto, Rahma Dewi e Nurkadri. "Relationship of Power, Waist Muscle Flexibility, and Power Muscle Legs Against Smash Volleyball For FIK UNM Makassar Students". Kinestetik : Jurnal Ilmiah Pendidikan Jasmani 6, n. 3 (30 settembre 2022): 560–67. http://dx.doi.org/10.33369/jk.v6i3.23732.
Testo completoAbstract (sommario):
Power Leg Muscle Power volleyball for FIK UNM Makassar students. The sample used in this study were FIK UNM Makassar students who took volleyball courses. Data analysis techniques used to test the hypothesis are normality test, linearity test, and correlation test. From the results of the first hypothesis correlation test, a significance value of 0.046 < 0.05 was obtained, so there was a significant relationship between power arm muscle smash. The results of the second hypothesis test have a significance value of 0.037 < 0.05, so there is a significant relationship between Waist Muscle Flexibility and Smash. The results of the third hypothesis test have a significance value of 0.032 < 0.05, so there is a significant relationship between Waist Muscle Flexibility and Smash. Based on the multiple correlation test in the summary model table, it is known that the magnitude of the relationship between arm muscle power, waist muscle flexibility and leg muscle power (simultaneously) on the smash results calculated by the correlation coefficient is 0.452, this indicates a moderate effect. Meanwhile, the simultaneous contribution or contribution of the arm muscle power variable with the flexibility of the waist muscles is 20.4% while 79.1% is determined by other variables.
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Wakeling, J. M., K. M. Kemp e I. A. Johnston. "The biomechanics of fast-starts during ontogeny in the common carp cyprinus carpio". Journal of Experimental Biology 202, n. 22 (15 novembre 1999): 3057–67. http://dx.doi.org/10.1242/jeb.202.22.3057.
Testo completoAbstract (sommario):
Common carp Cyprinus carpio L. were reared a constant temperature of 20 degrees C from the larval (7 mm total length) to the juvenile (80 mm) stage. Body morphology and white muscle mass distribution were measured. Fast-start escape responses were recorded using high-speed cinematography from which the velocities, accelerations and hydrodynamic power requirements were estimated. All three measures of fast-start performance increased during development. White muscle contraction regimes were calculated from changes in body shape during the fast-starts and used to predict the muscle force and power production for all longitudinal positions along the body. Scaling arguments predicted that increases in body length would constrain the fish to bend less rapidly because the cross-sectional muscle area, and hence force production, does not increase at the same rate as the inertial mass that resists bending. As predicted, the increases in body length resulted in decreases in muscle shortening velocity, and this coincided with increases in both the force and power produced by the muscles. The hydrodynamic efficiency, which relates the mechanical power produced by the muscles to the inertial power requirements in the direction of travel, showed no significant change during ontogeny. The increasing hydrodynamic power requirements were thus met by increases in the power available from the muscles. The majority of the increases in fast-start swimming performance during ontogeny can be explained by size-dependent increases in muscle power output. For all sizes, there was a decrease in muscle-mass-specific power output and an increase in muscle stress in a posterior direction along the body due to systematic variations in fibre strain. These changing strain regimes result in the central muscle bulk producing the majority of the power requirements during the fast-start, and this power is transmitted to the tail region of the fish and ultimately to the water via muscle in the caudal myotomes.
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Umam, Choirul, Oce Wiriawan e Edy Mintarto. "EFFECT OF EXERCISE BENCH PRESS AND SITTING CALF WITH CHEST PRESS AND LEG PRESS TO POWERARM MUSCLE AND POWER LIMB MUSCLES". JIPES - JOURNAL OF INDONESIAN PHYSICAL EDUCATION AND SPORT 3, n. 2 (28 dicembre 2017): 57–69. http://dx.doi.org/10.21009/jipes.032.05.
Testo completoAbstract (sommario):
This research aims to examine:1) How big the effectofbench press and sitting calf exercises to arm muscle power and leg muscle power; 2) How big the effect of chest press and leg press exercises to arm muscle power and leg muscle power; 3)How big the effect difference between bench press and sitting calf exercises and chest press and leg press exercises to to arm muscle power and leg muscle power. Research subject was boy student of SMA Negeri 1 Manyar as many 36 students, with age span 15-17 years which divided to three groups. Experiment group I received bench press and sitting calf while the second ones received chest press and leg press and the third experiment group performed activities according to daily routines. This type of research was applied quantitative research with quasi experimental research methods. The research design applied non-randomized control group pretest-postest design. And data analysis used were t-test and MANOVA. The data collecting process was using a medicine ball to obtain arm muscle power data and jump DF for leg muscle power during pretest and posttest. The results showed the difference between the pretest and posttest means of each group, namely: experimental group I for arm muscle power = 28.3 leg muscle power = 51.1. The second experiment group for arm muscle power = 45.9, leg muscle power = 78.2. Experiment Group III for arm muscle power = 13.3, leg muscle power = 27.1. Based on the above analysis, it can be concluded that there was an increase in all dependent variables for each experimental group after received bench press and sitting calf, chest press and leg press exercises, whereas chest press and leg press exercises were more effective at increasing arm muscle power and leg muscle strength
Keywords: Weight training, Bench Press, Calf Sitting, Chest Pres, Leg Press, Arm Muscles Power, Leg Muscle Power.
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Trappe, S., P. Gallagher, M. Harber, J. Carrithers, W. Evans e T. Trappe. "MUSCLE POWER WITH AGING". Medicine & Science in Sports & Exercise 34, n. 5 (maggio 2002): S98. http://dx.doi.org/10.1097/00005768-200205001-00544.
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Alexander, R. McNeill. "Flexing our muscle power". Nature 416, n. 6883 (aprile 2002): 793. http://dx.doi.org/10.1038/416793a.
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Eglseer, Doris, Ruth Poglitsch e Regina Elisabeth Roller-Wirnsberger. "Muscle power and nutrition". Zeitschrift für Gerontologie und Geriatrie 49, n. 2 (18 dicembre 2015): 115–19. http://dx.doi.org/10.1007/s00391-015-1008-7.
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Santos, Paulo D. G., João R. Vaz, Paulo F. Correia, Maria J. Valamatos, António P. Veloso e Pedro Pezarat-Correia. "Muscle Synergies Reliability in the Power Clean Exercise". Journal of Functional Morphology and Kinesiology 5, n. 4 (22 ottobre 2020): 75. http://dx.doi.org/10.3390/jfmk5040075.
Testo completoAbstract (sommario):
Muscle synergy extraction has been utilized to investigate muscle coordination in human movement, namely in sports. The reliability of the method has been proposed, although it has not been assessed previously during a complex sportive task. Therefore, the aim of the study was to evaluate intra- and inter-day reliability of a strength training complex task, the power clean, assessing participants’ variability in the task across sets and days. Twelve unexperienced participants performed four sets of power cleans in two test days after strength tests, and muscle synergies were extracted from electromyography (EMG) data of 16 muscles. Three muscle synergies accounted for almost 90% of variance accounted for (VAF) across sets and days. Intra-day VAF, muscle synergy vectors, synergy activation coefficients and individual EMG profiles showed high similarity values. Inter-day muscle synergy vectors had moderate similarity, while the variables regarding temporal activation were still strongly related. The present findings revealed that the muscle synergies extracted during the power clean remained stable across sets and days in unexperienced participants. Thus, the mathematical procedure for the extraction of muscle synergies through nonnegative matrix factorization (NMF) may be considered a reliable method to study muscle coordination adaptations from muscle strength programs.
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Roberts, Thomas J., e Emanuel Azizi. "The series-elastic shock absorber: tendons attenuate muscle power during eccentric actions". Journal of Applied Physiology 109, n. 2 (agosto 2010): 396–404. http://dx.doi.org/10.1152/japplphysiol.01272.2009.
Testo completoAbstract (sommario):
Elastic tendons can act as muscle power amplifiers or energy-conserving springs during locomotion. We used an in situ muscle-tendon preparation to examine the mechanical function of tendons during lengthening contractions, when muscles absorb energy. Force, length, and power were measured in the lateral gastrocnemius muscle of wild turkeys. Sonomicrometry was used to measure muscle fascicle length independently from muscle-tendon unit (MTU) length, as measured by a muscle lever system (servomotor). A series of ramp stretches of varying velocities was applied to the MTU in fully activated muscles. Fascicle length changes were decoupled from length changes imposed on the MTU by the servomotor. Under most conditions, muscle fascicles shortened on average, while the MTU lengthened. Energy input to the MTU during the fastest lengthenings was −54.4 J/kg, while estimated work input to the muscle fascicles during this period was only −11.24 J/kg. This discrepancy indicates that energy was first absorbed by elastic elements, then released to do work on muscle fascicles after the lengthening phase of the contraction. The temporary storage of energy by elastic elements also resulted in a significant attenuation of power input to the muscle fascicles. At the fastest lengthening rates, peak instantaneous power input to the MTU reached −2,143.9 W/kg, while peak power input to the fascicles was only −557.6 W/kg. These results demonstrate that tendons may act as mechanical buffers by limiting peak muscle forces, lengthening rates, and power inputs during energy-absorbing contractions.
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Robertson, D. G. E., Jean-Marie J. Wilson e Taunya A. St Pierre. "Lower Extremity Muscle Functions during Full Squats". Journal of Applied Biomechanics 24, n. 4 (novembre 2008): 333–39. http://dx.doi.org/10.1123/jab.24.4.333.
Testo completoAbstract (sommario):
The purpose of this research was to determine the functions of the gluteus maximus, biceps femoris, semitendinosus, rectus femoris, vastus lateralis, soleus, gastrocnemius, and tibialis anterior muscles about their associated joints during full (deep-knee) squats. Muscle function was determined from joint kinematics, inverse dynamics, electromyography, and muscle length changes. The subjects were six experienced, male weight lifters. Analyses revealed that the prime movers during ascent were the monoarticular gluteus maximus and vasti muscles (as exemplified by vastus lateralis) and to a lesser extent the soleus muscles. The biarticular muscles functioned mainly as stabilizers of the ankle, knee, and hip joints by working eccentrically to control descent or transferring energy among the segments during ascent. During the ascent phase, the hip extensor moments of force produced the largest powers followed by the ankle plantar flexors and then the knee extensors. The hip and knee extensors provided the initial bursts of power during ascent with the ankle extensors and especially a second burst from the hip extensors adding power during the latter half of the ascent.
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Josephson, Robert K., Jean G. Malamud e Darrell R. Stokes. "The efficiency of an asynchronous flight muscle from a beetle". Journal of Experimental Biology 204, n. 23 (1 dicembre 2001): 4125–39. http://dx.doi.org/10.1242/jeb.204.23.4125.
Testo completoAbstract (sommario):
SUMMARYMechanical power output and metabolic power input were measured from an asynchronous flight muscle, the basalar muscle of the beetle Cotinus mutabilis. Mechanical power output was determined using the work loop technique and metabolic power input by monitoring CO2 production or both CO2 production and O2 consumption. At 35°C, and with conditions that maximized power output (60 Hz sinusoidal strain, optimal muscle length and strain amplitude, 60 Hz stimulation frequency), the peak mechanical power output during a 10 s burst was approximately 140 W kg–1, the respiratory coefficient 0.83 and the muscle efficiency 14–16 %. The stimulus intensity used was the minimal required to achieve a maximal isometric tetanus. Increasing or decreasing the stimulus intensity from this level changed mechanical power output but not efficiency, indicating that the efficiency measurements were not contaminated by excitation of muscles adjacent to that from which the mechanical recordings were made. The CO2 produced during an isometric tetanus was approximately half that during a bout of similar stimulation but with imposed sinusoidal strain and work output, suggesting that up to 50 % of the energy input may go to muscle activation costs. Reducing the stimulus frequency to 30 Hz from its usual value of 60 Hz reduced mechanical power output but had no significant effect on efficiency. Increasing the frequency of the sinusoidal strain from 60 to 90 Hz reduced power output but not CO2 consumption; hence, there was a decline in efficiency. The respiratory coefficient was the same for 10 s and 30 s bursts of activity, suggesting that there was no major change in the fuel used over this time range.The mass-specific mechanical power output and the efficiency of the beetle muscle were each 2–3 times greater than values measured in previous studies, using similar techniques, from locust flight muscles, which are synchronous muscles. These results support the hypothesis that asynchronous flight muscles have evolved in several major insect taxa because they can provide greater power output and are more efficient than are synchronous muscles for operation at the high frequencies of insect flight.
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James, Rob S., Robbie S. Wilson e Graham N. Askew. "Effects of caffeine on mouse skeletal muscle power output during recovery from fatigue". Journal of Applied Physiology 96, n. 2 (febbraio 2004): 545–52. http://dx.doi.org/10.1152/japplphysiol.00696.2003.
Testo completoAbstract (sommario):
The effects of 10 mM (high) and 70 μM (physiologically relevant) caffeine on force, work output, and power output of isolated mouse extensor digitorum longus (EDL) and soleus muscles were investigated in vitro during recovery from fatigue at 35°C. To monitor muscle performance during recovery from fatigue, we regularly subjected the muscle to a series of cyclical work loops. Force, work, and power output during shortening were significantly higher after treatment with 10 mM caffeine, probably as a result of increased Ca2+ release from the sarcoplasmic reticulum. However, the work required to relengthen the muscle also increased in the presence of 10 mM caffeine. This was due to a slowing of relaxation and an increase in muscle stiffness. The combination of increased work output during shortening and increased work input during lengthening had different effects on the two muscles. Net power output of mouse soleus muscle decreased as a result of 10 mM caffeine exposure, whereas net power output of the EDL muscle showed a transient, significant increase. Treatment with 70 μM caffeine had no significant effect on force, work, or power output of EDL or soleus muscles, suggesting that the plasma concentrations found when caffeine is used to enhance performance in human athletes might not directly affect the contractile performance of fatigued skeletal muscle.
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Rome, L. C., D. M. Swank e D. J. Coughlin. "The influence of temperature on power production during swimming. II. Mechanics of red muscle fibres in vivo". Journal of Experimental Biology 203, n. 2 (15 gennaio 2000): 333–45. http://dx.doi.org/10.1242/jeb.203.2.333.
Testo completoAbstract (sommario):
We found previously that scup (Stenotomus chrysops) reduce neither their stimulation duration nor their tail-beat frequency to compensate for the slow relaxation rates of their muscles at low swimming temperatures. To assess the impact of this ‘lack of compensation’ on power generation during swimming, we drove red muscle bundles under their in vivo conditions and measured the resulting power output. Although these in vivo conditions were near the optimal conditions for much of the muscle at 20 degrees C, they were far from optimal at 10 degrees C. Accordingly, in vivo power output was extremely low at 10 degrees C. Although at 30 cm s(−)(1), muscles from all regions of the fish generated positive work, at 40 and 50 cm s(−)(1), only the POST region (70 % total length) generated positive work, and that level was low. This led to a Q(10) of 4–14 in the POST region (depending on swimming speed), and extremely high or indeterminate Q(10) values (if power at 10 degrees C is zero or negative, Q(10) is indeterminate) for the other regions while swimming at 40 or 50 cm s(−)(1). To assess whether errors in measurement of the in vivo conditions could cause artificially reduced power measurements at 10 degrees C, we drove muscle bundles through a series of conditions in which the stimulation duration was shortened and other parameters were made closer to optimal. This sensitivity analysis revealed that the low power output could not be explained by realistic levels of systematic or random error. By integrating the muscle power output over the fish's mass and comparing it with power requirements for swimming, we conclude that, although the fish could swim at 30 cm s(−)(1) with the red muscle alone, it is very unlikely that it could do so at 40 and 50 cm s(−)(1), thus raising the question of how the fish powers swimming at these speeds. By integrating in vivo pink muscle power output along the length of the fish, we obtained the surprising finding that, at 50 cm s(−)(1), the pink muscle (despite having one-third the mass) contributes six times more power to swimming than does the red muscle. Thus, in scup, pink muscle is crucial for powering swimming at low temperatures. This overall analysis shows that Q(10) values determined in experiments on isolated tissue under arbitrarily selected conditions can be very different from Q(10) values in vivo, and therefore that predicting whole-animal performance from these isolated tissue experiments may lead to qualitatively incorrect conclusions. To make a meaningful assessment of the effects of temperature on muscle and locomotory performance, muscle performance must be studied under the conditions at which the muscle operates in vivo.
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Josephson, R. K., J. G. Malamud e D. R. Stokes. "Power output by an asynchronous flight muscle from a beetle". Journal of Experimental Biology 203, n. 17 (1 settembre 2000): 2667–89. http://dx.doi.org/10.1242/jeb.203.17.2667.
Testo completoAbstract (sommario):
The basalar muscle of the beetle Cotinus mutabilis is a large, fibrillar flight muscle composed of approximately 90 fibers. The paired basalars together make up approximately one-third of the mass of the power muscles of flight. Changes in twitch force with changing stimulus intensity indicated that a basalar muscle is innervated by at least five excitatory axons and at least one inhibitory axon. The muscle is an asynchronous muscle; during normal oscillatory operation there is not a 1:1 relationship between muscle action potentials and contractions. During tethered flight, the wing-stroke frequency was approximately 80 Hz, and the action potential frequency in individual motor units was approximately 20 Hz. As in other asynchronous muscles that have been examined, the basalar is characterized by high passive tension, low tetanic force and long twitch duration. Mechanical power output from the basalar muscle during imposed, sinusoidal strain was measured by the work-loop technique. Work output varied with strain amplitude, strain frequency, the muscle length upon which the strain was superimposed, muscle temperature and stimulation frequency. When other variables were at optimal values, the optimal strain for work per cycle was approximately 5%, the optimal frequency for work per cycle approximately 50 Hz and the optimal frequency for mechanical power output 60–80 Hz. Optimal strain decreased with increasing cycle frequency and increased with muscle temperature. The curve relating work output and strain was narrow. At frequencies approximating those of flight, the width of the work versus strain curve, measured at half-maximal work, was 5% of the resting muscle length. The optimal muscle length for work output was shorter than that at which twitch and tetanic tension were maximal. Optimal muscle length decreased with increasing strain. The curve relating work output and muscle length, like that for work versus strain, was narrow, with a half-width of approximately 3 % at the normal flight frequency. Increasing the frequency with which the muscle was stimulated increased power output up to a plateau, reached at approximately 100 Hz stimulation frequency (at 35 degrees C). The low lift generated by animals during tethered flight is consistent with the low frequency of muscle action potentials in motor units of the wing muscles. The optimal oscillatory frequency for work per cycle increased with muscle temperature over the temperature range tested (25–40 degrees C). When cycle frequency was held constant, the work per cycle rose to an optimum with increasing temperature and then declined. We propose that there is a temperature optimum for work output because increasing temperature increases the shortening velocity of the muscle, which increases the rate of positive work output during shortening, but also decreases the durations of the stretch activation and shortening deactivation that underlie positive work output, the effect of temperature on shortening velocity being dominant at lower temperatures and the effect of temperature on the time course of activation and deactivation being dominant at higher temperatures. The average wing-stroke frequency during free flight was 94 Hz, and the thoracic temperature was 35 degrees C. The mechanical power output at the measured values of wing-stroke frequency and thoracic temperature during flight, and at optimal muscle length and strain, averaged 127 W kg(−1)muscle, with a maximum value of 200 W kg(−1). The power output from this asynchronous flight muscle was approximately twice that measured with similar techniques from synchronous flight muscle of insects, supporting the hypothesis that asynchronous operation has been favored by evolution in flight systems of different insect groups because it allows greater power output at the high contraction frequencies of flight.
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Koloway, Christie Brenda Gabriella, Joshua Runtuwene e Fima Lanra Fredrik Gerald Langi. "Kekuatan Otot Perut, Daya Ledak Otot Lengan, Tinggi Lompatan dan Hasil Pukulan Smash Penuh pada Atlet Bulutangkis". Sam Ratulangi Journal of Public Health 2, n. 1 (29 marzo 2021): 022. http://dx.doi.org/10.35801/srjoph.v2i1.33887.
Testo completoAbstract (sommario):
Background: Badminton is one of the most popular sports in the world, including in Indonesia. Badminton has been around since the 1930s. The strength of the abdominal muscles contributes to a full smash during hitting. Explosive power is an important biometric ability in sports activities, because the explosive power will determine how hard people can hit, kick, jump, run and so on. Jump height is a component of physical fitness to measure leg muscle power. The purpose of this study was to analyze the correlation between abdominal muscle strength, arm muscle explosive power, jump height and the result of a full smash in badminton athletes. Methods: This is a correlational research with cross-sectional approach. This research in the Badminton Field of SMK N 2 Manado in November 2020, using an analytical method with a cross-sectional design. The population is all PB athletes in Manado. The research instrument used was for abdominal muscle strength (sit-ups), for the explosive power of the arm muscles (two hand medicine ball put test), for the height of the jump (vertical jump test), the results of the smash. Data analysis used two stages, namely univariate and bivariate. Results: The results showed that the most distributed respondents based on male sex (62%), the average value of abdominal muscle strength (25.72), the average value of arm muscle explosive power (1.52), the average value – the average jump height (2), and the average value of the smash results (16.44). The results of bivariate analysis showed that there was no relationship between abdominal muscle strength (rcount = 0.211 < rtable= 0.273), arm muscle explosive power (rcount = 0.020) < rtable = 0.273), and jump height (rcount = -0.008 < rtable = 0.273) with a smash hit. Conclusion: That can be conclude there is no correlation between abdominal muscle strength, arm muscle explosive power, and jump height with the results of smash hits.
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Permana, Dwinda Abi, Nining Widyah Kusnanik, Nurhasan Nurhasan, Hari Setijono, Muhammad Zainal Arifin e Septyaningrum Putri Purwoto. "Enhancing Strength, Leg Muscle Explosive Power, and Muscle Hypertrophy Using Hurdle-Box Jump Plyometric". Teorìâ ta Metodika Fìzičnogo Vihovannâ 22, n. 1 (25 marzo 2022): 113–20. http://dx.doi.org/10.17309/tmfv.2022.1.16.
Testo completoAbstract (sommario):
The study purpose was to examine and analyze the effect of developing a hurdle-box jump plyometric model on muscle strength, explosive power, and hypertrophy.
Materials and methods. This research was an experimental study with a two group pretest-posttest design. The sample in this study was male sub-elite athletes from various sports aged 15-17 years who were selected at random sampling totaling 22 athletes, divided into 2 (two) groups, the treatment group using plyometric hurdle-box jump development (n = 11) and the control group using plyometric barrier hops (n = 11).
Results. The results showed that: (1) there was a significant effect of plyometric hurdle-box jump exercise on strength, leg muscle explosive power, and muscle hypertrophy, (2) there was a significant effect of plyometric barrier hops exercise (control group) on strength, leg muscles explosive power, and muscle hypertrophy, and (3) there was a significant difference between plyometric hurdle-box jump exercises and plyometric barrier hops exercises (control group) on strength, leg muscle explosive power, and muscle hypertrophy.
Conclusions. The percentage increase in pretest and posttest scores on strength, leg muscle explosive power, and muscle hypertrophy showed that the hurdle-box jump plyometric exercise group was better than the control group (barrier hops).
35
Trumble, D. R., e J. A. Magovern. "Ergometric studies of untrained skeletal muscle demonstrate feasibility of muscle-powered cardiac assistance". Journal of Applied Physiology 77, n. 4 (1 ottobre 1994): 2036–41. http://dx.doi.org/10.1152/jappl.1994.77.4.2036.
Testo completoAbstract (sommario):
The feasibility of biomechanical circulatory assistance hinges on the capacity of skeletal muscle to generate significant hemodynamic work. This study quantifies linear contractile energetics via a customized hydraulic ergometer. Six normal canine latissimus dorsi (LD) muscles (200 +/- 25 g) were evaluated. The muscles were not mobilized; thereby their collateral circulation was preserved. The humeral insertion of the LD muscle was transected and connected to the ergometer. Preload was adjusted to return the LD muscle to its in situ length, and one pulse train was delivered every second. The resulting contractions generated peak pressures of 134 +/- 17 mmHg with mean pressures during shortening of 102 +/- 12 mmHg. Flow rates averaged 5.45 +/- 0.26 l/min. Mechanical work output was calculated at 1.14 +/- 0.18 J/contraction, yielding an average power production of 4.57 +/- 0.72 W during shortening. Continuous LD output power, measured at 5.76 +/- 0.90 mW/g, compares favorably with the 3.48 mW/g typically generated by a 350-g human heart. We therefore conclude that skeletal muscle of sufficient mass can sustain work rates suitable for cardiac assistance despite the 50% power losses typically experienced after muscle training.
36
Barrett, Ursula, e Drew Harrison. "Comparing Muscle Function of Children and Adults: Effects of Scaling for Muscle Size". Pediatric Exercise Science 14, n. 4 (novembre 2002): 369–76. http://dx.doi.org/10.1123/pes.14.4.369.
Testo completoAbstract (sommario):
This study examined the force-velocity and power-velocity relationships of the quadriceps muscles of children and adults. Measurements of muscle function were collected using the Con-Trex isokinetic dynamometer. Twenty adults and twenty children performed maximal effort knee extensions at nine different velocities. The mean force-velocity curves of children and adults revealed obvious differences between the groups. The curves remained different following corrections of torque for CSA and velocity for length. ANOVA revealed significant differences in the uncorrected values of power between the two groups. When power values were corrected for lean thigh muscle volume, no significant differences were found between the groups. These findings suggest that differences in muscle strength between children and adults are a function of muscle size and imply that muscle function remains relatively unchanged from childhood to early adulthood.
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Aerts, P. "Vertical jumping in Galago senegalensis: the quest for an obligate mechanical power amplifier". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 353, n. 1375 (29 ottobre 1998): 1607–20. http://dx.doi.org/10.1098/rstb.1998.0313.
Testo completoAbstract (sommario):
Bushbabies ( Galago senegalensis ) are renowned for their phenomenal jumping capacity. It was postulated that mechanical power amplification must be involved. Dynamic analysis of the vertical jumps performed by two bushbabies confirms the need for a power amplifier. Inverse dynamics coupled to a geometric musculo–skeletal model were used to elucidate the precise nature of the mechanism powering maximal vertical jumps. Most of the power required for jumping is delivered by the vastus muscle–tendon systems (knee extensor). Comparison with the external joint–powers revealed, however, an important power transport from this extensor (about 65%) to the ankle and the midfoot via the bi–articular calf muscles. Peak power output likely implies elastic recoil of the complex aponeurotic system of the vastus muscle. Patterns of changes in length and tension of the muscle–tendon complex during different phases of the jump were found which provide strong evidence for substantial power amplification (times 15). It is argued here that the multiple internal connective tissue sheets and attachment structures of the well–developed bundles of the vastus muscle become increasingly stretched during preparatory crouching and throughout the extension phase, except for the last 13 ms of the push–off (i.e. when power requirements peak). Then, tension in the knee extensors abruptly falls from its maximum, allowing the necessary fast recoil of the tensed tendon structures to occur.
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James, R. S., V. M. Cox, I. S. Young, J. D. Altringham e D. F. Goldspink. "Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation". Journal of Applied Physiology 83, n. 2 (1 agosto 1997): 398–406. http://dx.doi.org/10.1152/jappl.1997.83.2.398.
Testo completoAbstract (sommario):
James, R. S., V. M. Cox, I. S. Young, J. D. Altringham, and D. F. Goldspink Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation. J. Appl. Physiol. 83(2): 398–406, 1997.—The work loop technique was used to measure the mechanical performance in situ of the latissimus dorsi (LD) muscles of rabbits maintained under fentanyl anesthesia. After 3 wk of incrementally applied stretch the LD muscles were 36% heavier, but absolute power output (195 mW/muscle) was not significantly changed relative to that of external control muscle (206 mW). In contrast, continuous 10-Hz electrical stimulation reduced power output per kilogram of muscle >75% after 3 or 6 wk and muscle mass by 32% after 6 wk. When combined, stretch and 10-Hz electrical stimulation preserved or increased the mass of the treated muscles but failed to prevent an 80% loss in maximum muscle power. However, this combined treatment increased fatigue resistance to a greater degree than electrical stimulation alone. These stretched/stimulated muscles, therefore, are more suitable for cardiomyoplasty. Nonetheless, further work will be necessary to find an ideal training program for this surgical procedure.
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Roberts, Thomas J. "Some Challenges of Playing with Power: Does Complex Energy Flow Constrain Neuromuscular Performance?" Integrative and Comparative Biology 59, n. 6 (26 giugno 2019): 1619–28. http://dx.doi.org/10.1093/icb/icz108.
Testo completoAbstract (sommario):
Abstract Many studies of the flow of energy between the body, muscles, and elastic elements highlight advantages of the storage and recovery of elastic energy. The spring-like action of structures associated with muscles allows for movements that are less costly, more powerful and safer than would be possible with contractile elements alone. But these actions also present challenges that might not be present if the pattern of energy flow were simpler, for example, if power were always applied directly from muscle to motions of the body. Muscle is under the direct control of the nervous system, and precise modulation of activity can allow for finely controlled displacement and force. Elastic structures deform under load in a predictable way, but are not under direct control, thus both displacement and the flow of energy act at the mercy of the mechanical interaction of muscle and forces associated with movement. Studies on isolated muscle-tendon units highlight the challenges of controlling such systems. A carefully tuned activation pattern is necessary for effective cycling of energy between tendon and the environment; most activation patterns lead to futile cycling of energy between tendon and muscle. In power-amplified systems, “elastic backfire” sometimes occurs, where energy loaded into tendon acts to lengthen active muscles, rather than accelerate the body. Classic models of proprioception that rely on muscle spindle organs for sensing muscle and joint displacement illustrate how elastic structures might influence sensory feedback by decoupling joint movement from muscle fiber displacements. The significance of the complex flow of energy between muscles, elastic elements and the body for neuromotor control is worth exploring.
40
Rome, L. C. "Influence of temperature on muscle recruitment and muscle function in vivo". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 259, n. 2 (1 agosto 1990): R210—R222. http://dx.doi.org/10.1152/ajpregu.1990.259.2.r210.
Testo completoAbstract (sommario):
Temperature has a large influence on the maximum velocity of shortening (Vmax) and maximum power output of muscle (Q10 = 1.5-3). In some animals, maximum performance and maximum sustainable performance show large temperature sensitivities, because these parameters are dependent solely on mechanical power output of the muscles. The mechanics of locomotion (sarcomere length excursions and muscle-shortening velocities, V) at a given speed, however, are precisely the same at all temperatures. Animals compensate for the diminished power output of their muscles at low temperatures by compressing their recruitment order into a narrower range of locomotor speeds, that is, recruiting more muscle fibers and faster fiber types at a given speed. By examining V/Vmax, I calculate that fish at 10 degrees C must recruit 1.53-fold greater fiber cross section than at 20 degrees C. V/Vmax also appears to be an important design constraint in muscle. It sets the lowest V and the highest V over which a muscle can be used effectively. Because the Vmax of carp slow red muscle has a Q10 of 1.6 between 10 and 20 degrees C, the slow aerobic fibers can be used over a 1.6-fold greater range of swim speeds at the warmer temperature. In some species of fish, Vmax can be increased during thermal acclimation, enabling animals to swim at higher speeds.
41
Gabaldón, Annette M., Frank E. Nelson e Thomas J. Roberts. "Relative shortening velocity in locomotor muscles: turkey ankle extensors operate at low V/Vmax". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 294, n. 1 (gennaio 2008): R200—R210. http://dx.doi.org/10.1152/ajpregu.00473.2007.
Testo completoAbstract (sommario):
The force-velocity properties of skeletal muscle have an important influence on locomotor performance. All skeletal muscles produce less force the faster they shorten and typically develop maximal power at velocities of ∼30% of maximum shortening velocity (Vmax). We used direct measurements of muscle mechanical function in two ankle extensor muscles of wild turkeys to test the hypothesis that during level running muscles operate at velocities that favor force rather than power. Sonomicrometer measurements of muscle length, tendon strain-gauge measurements of muscle force, and bipolar electromyographs were taken as animals ran over a range of speeds and inclines. These measurements were integrated with previously measured values of muscle Vmax for these muscles to calculate relative shortening velocity (V/Vmax). At all speeds for level running the V/Vmax values of the lateral gastrocnemius and the peroneus longus were low (<0.05), corresponding to the region of the force-velocity relationship where the muscles were capable of producing 90% of peak isometric force but only 35% of peak isotonic power. V/Vmax increased in response to the demand for mechanical power with increases in running incline and decreased to negative values to absorb energy during downhill running. Measurements of integrated electromyograph activity indicated that the volume of muscle required to produce a given force increased from level to uphill running. This observation is consistent with the idea that V/Vmax is an important determinant of locomotor cost because it affects the volume of muscle that must be recruited to support body weight.
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Syme, Douglas A., e Robert E. Shadwick. "Effects of longitudinal body position and swimming speed on mechanical power of deep red muscle from skipjack tuna (Katsuwonus pelamis)". Journal of Experimental Biology 205, n. 2 (15 gennaio 2002): 189–200. http://dx.doi.org/10.1242/jeb.205.2.189.
Testo completoAbstract (sommario):
SUMMARY The mechanical power output of deep, red muscle from skipjack tuna (Katsuwonus pelamis) was studied to investigate (i) whether this muscle generates maximum power during cruise swimming, (ii) how the differences in strain experienced by red muscle at different axial body locations affect its performance and (iii) how swimming speed affects muscle work and power output. Red muscle was isolated from approximately mid-way through the deep wedge that lies next to the backbone; anterior (0.44 fork lengths, ANT) and posterior (0.70 fork lengths, POST) samples were studied. Work and power were measured at 25°C using the work loop technique. Stimulus phases and durations and muscle strains (±5.5 % in ANT and ±8 % in POST locations) experienced during cruise swimming at different speeds were obtained from previous studies and used during work loop recordings. In addition, stimulus conditions that maximized work were determined. The stimulus durations and phases yielding maximum work decreased with increasing cycle frequency (analogous to tail-beat frequency), were the same at both axial locations and were almost identical to those used by the fish during swimming, indicating that the muscle produces near-maximal work under most conditions in swimming fish. While muscle in the posterior region undergoes larger strain and thus produces more mass-specific power than muscle in the anterior region, when the longitudinal distribution of red muscle mass is considered, the anterior muscles appear to contribute approximately 40 % more total power. Mechanical work per length cycle was maximal at a cycle frequency of 2–3 Hz, dropping to near zero at 15 Hz and by 20–50 % at 1 Hz. Mechanical power was maximal at a cycle frequency of 5 Hz, dropping to near zero at 15 Hz. These fish typically cruise with tail-beat frequencies of 2.8–5.2 Hz, frequencies at which power from cyclic contractions of deep red muscles was 75–100 % maximal. At any given frequency over this range, power using stimulation conditions recorded from swimming fish averaged 93.4±1.65 % at ANT locations and 88.6±2.08 % at POST locations (means ± s.e.m., N=3–6) of the maximum using optimized conditions. When cycle frequency was held constant (4 Hz) and strain amplitude was increased, work and power increased similarly in muscles from both sample sites; work and power increased 2.5-fold when strain was elevated from ±2 to ±5.5 %, but increased by only approximately 12 % when strain was raised further from ±5.5 to ±8 %. Taken together, these data suggest that red muscle fibres along the entire body are used in a similar fashion to produce near-maximal mechanical power for propulsion during normal cruise swimming. Modelling suggests that the tail-beat frequency at which power is maximal (5 Hz) is very close to that used at the predicted maximum aerobic swimming speed (5.8 Hz) in these fish.
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Syme, D. A. "The efficiency of frog ventricular muscle." Journal of Experimental Biology 197, n. 1 (1 dicembre 1994): 143–64. http://dx.doi.org/10.1242/jeb.197.1.143.
Testo completoAbstract (sommario):
Mechanical power and oxygen consumption (VO2) were measured simultaneously from isolated segments of trabecular muscle from the frog (Rana pipiens) ventricle. Power was measured using the work-loop technique, in which bundles of trabeculae were subjected to cyclic, sinusoidal length change and phasic stimulation. VO2 was measured using a polarographic O2 electrode. Both mechanical power and VO2 increased with increasing cycle frequency (0.4-0.9 Hz), with increasing muscle length and with increasing strain (= shortening, range 0-25% of resting length). Net efficiency, defined as the ratio of mechanical power output to the energy equivalent of the increase in VO2 above resting level, was independent of cycle frequency and increased from 8.1 to 13.0% with increasing muscle length, and from 0 to 13% with increasing strain, in the ranges examined. Delta efficiency, defined as the slope of the line relating mechanical power output to the energy equivalent of VO2, was 24-43%, similar to that reported from studies using intact hearts. The cost of increasing power output was greater if power was increased by increasing cycle frequency or muscle length than if it was increased by increasing strain. The results suggest that the observation that pressure-loading is more costly than volume-loading is inherent to these muscle fibres and that frog cardiac muscle is, if anything, less efficient than most skeletal muscles studied thus far.
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Bobbert, Maarten F., L. J. Richard Casius, Stephan van der Zwaard e Richard T. Jaspers. "Effect of vasti morphology on peak sprint cycling power of a human musculoskeletal simulation model". Journal of Applied Physiology 128, n. 2 (1 febbraio 2020): 445–55. http://dx.doi.org/10.1152/japplphysiol.00674.2018.
Testo completoAbstract (sommario):
Fascicle length of m. vastus lateralis in cyclists has been shown to correlate positively with peak sprint cycling power normalized for lean body mass. We investigated whether vasti morphology affects sprint cycling power via force-length and force-velocity relationships. We simulated isokinetic sprint cycling at pedaling rates ranging from 40 to 150 rpm with a forward dynamic model of the human musculoskeletal system actuated by eight leg muscles. Input of the model was muscle stimulation over time, which was optimized to maximize the average power output over a pedal cycle. This was done for a reference model and for models in which the vasti had equal volume but different morphology. It was found that models with longer muscle fibers but a reduced physiological cross-sectional area of the vasti produced a higher sprint cycling power. This was partly explained by better alignment of the peak power-pedaling rate curve of the vasti with the corresponding curves of the other leg muscles. The highest sprint cycling power was achieved in a model in which the increase in muscle fiber length of the vasti was accompanied by a concomitant shift in optimum knee angle. It was concluded that muscle mechanics can partly explain the positive correlations between fascicle length of m. vastus lateralis and normalized peak sprint cycling power. It should be investigated whether muscle fiber length of the vasti and optimum knee angle are suitable training targets for athletes who want to concurrently improve their sprint and endurance cycling performance. NEW & NOTEWORTHY We simulated isokinetic sprint cycling at pedaling rates ranging from 40 to 150 rpm with a forward dynamic model of the human musculoskeletal system actuated by eight leg muscles. We selectively modified vasti morphology: we lengthened the muscle fibers and reduced the physiological cross-sectional area. The modified model was able to produce a higher sprint cycling power.
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Choi, Seung Jun, e Jeffrey J. Widrick. "Combined effects of fatigue and eccentric damage on muscle power". Journal of Applied Physiology 107, n. 4 (ottobre 2009): 1156–64. http://dx.doi.org/10.1152/japplphysiol.00403.2009.
Testo completoAbstract (sommario):
Many physical activities can induce both transient and long-lasting muscle dysfunction. The separate and interactive effects of short-term fatigue and long-lasting contraction-induced damage were evaluated in an in vitro mouse soleus preparation (35°C) using the work loop technique. Repetitive fatiguing work loops reduced positive work (work produced by the muscle), increased negative work (work required to reextend the muscle), and reduced cyclical power (net work/time) immediately after treatment. These changes were readily reversible. The fatigue treatment had no long-term effects on optimal muscle length ( Lo) and isometric force (Po). High strain lengthening work loops, where the muscle contracted eccentrically, resulted in both immediate and long-lasting positive work, power, and Po deficits as well as a shift in Lo to longer lengths. When the treatments were combined, i.e., fatigued muscles subjected to eccentric activity, the immediate power deficit exceeded the sum of the power deficits noted for the other two treatments. Much of this effect was due to an exaggerated rise in negative work. However, in the long term, power and Po deficits and the shift in Lo were reduced compared with the damage-only treatment. These results show that 1) the immediate effects of combined fatigue and damage on cyclical power are synergistic, in large part because of a reduced ability of the muscle to relax; and 2) fatigued muscles are less susceptible to long-term contraction-induced dysfunction. Fatigue may protect against long-term damage by reducing the probability that sarcomeres are lengthened beyond myofilament overlap.
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FUKUI, Tsutomu. "Sports Injury and Muscle Power." Rigakuryoho Kagaku 18, n. 1 (2003): 29–34. http://dx.doi.org/10.1589/rika.18.29.
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Lanza, I. R., T. F. Towse, D. Bartholomew, G. E. Caldwell e J. A. Kent-Braun. "MUSCLE TORQUE, VELOCITY AND POWER". Medicine & Science in Sports & Exercise 34, n. 5 (maggio 2002): S98. http://dx.doi.org/10.1097/00005768-200205001-00545.
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Gould, Paula. "Energetic fuels provide muscle power". Materials Today 9, n. 5 (maggio 2006): 16. http://dx.doi.org/10.1016/s1369-7021(06)71482-1.
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Verschuren, Olaf, e Tim Takken. "The Muscle Power Sprint Test". Journal of Physiotherapy 60, n. 4 (dicembre 2014): 239. http://dx.doi.org/10.1016/j.jphys.2014.08.001.
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Matsuura, Nobuyuki. "Muscle power during intravenous sedation". Japanese Dental Science Review 53, n. 4 (novembre 2017): 125–33. http://dx.doi.org/10.1016/j.jdsr.2017.02.001.
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